From 6ab36ca992441f7353840c70fc91d99a500a940e Mon Sep 17 00:00:00 2001
From: Glenn Elliott <gelliott@cs.unc.edu>
Date: Wed, 18 Apr 2012 16:24:56 -0400
Subject: Fixed and tested aff-aware KFMLP. (finally!)

---
 litmus/gpu_affinity.c | 87 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 55 insertions(+), 32 deletions(-)

(limited to 'litmus/gpu_affinity.c')

diff --git a/litmus/gpu_affinity.c b/litmus/gpu_affinity.c
index 43171390bed7..87349fe10a9b 100644
--- a/litmus/gpu_affinity.c
+++ b/litmus/gpu_affinity.c
@@ -5,15 +5,16 @@
 #include <litmus/litmus.h>
 #include <litmus/gpu_affinity.h>
 
-static void update_estimate(feedback_est_t* fb, fp_t* a, fp_t* b, lt_t observed)
+#define OBSERVATION_CAP 2*1e9
+
+static void update_estimate(feedback_est_t* fb, fp_t a, fp_t b, lt_t observed)
 {
 	fp_t err, new;
-	fp_t actual = _frac(observed, 1); // observed is in ns, so beware of overflow!
+	fp_t actual = _integer_to_fp(observed);
 	
 	err = _sub(actual, fb->est);
-	new = _add(_mul(*a, err),
-			   _mul(*b, fb->accum_err));
-	
+	new = _add(_mul(a, err), _mul(b, fb->accum_err));
+
 	fb->est = new;
 	fb->accum_err = _add(fb->accum_err, err);
 }
@@ -22,47 +23,69 @@ void update_gpu_estimate(struct task_struct *t, lt_t observed)
 {
 	feedback_est_t *fb = &(tsk_rt(t)->gpu_migration_est[tsk_rt(t)->gpu_migration]);
 	
-	TRACE_TASK(t, "GPU est update before (dist = %d): %d.%d\n", 
-			   tsk_rt(t)->gpu_migration,
-			   _fp_to_integer(fb->est),
-			   _point(fb->est));
-	
-	update_estimate(fb,
-					&tsk_rt(t)->gpu_fb_param_a,
-					&tsk_rt(t)->gpu_fb_param_b,
-					observed);
+	WARN_ON(tsk_rt(t)->gpu_migration > MIG_LAST);
 	
-	TRACE_TASK(t, "GPU est update after (dist = %d): %d.%d\n", 
+	if(unlikely(fb->est.val == 0)) {
+		// kludge-- cap observed values to prevent whacky estimations.
+		// whacky stuff happens during the first few jobs.
+		if(unlikely(observed > OBSERVATION_CAP)) {
+			TRACE_TASK(t, "Crazy observation was capped: %llu -> %llu\n",
+					   observed, OBSERVATION_CAP);
+			observed = OBSERVATION_CAP;
+		}		
+		
+		// take the first observation as our estimate
+		// (initial value of 0 was bogus anyhow)
+		fb->est = _integer_to_fp(observed);
+		fb->accum_err = _div(fb->est, _integer_to_fp(2));  // ...seems to work.
+	}
+	else {
+		update_estimate(fb,
+						tsk_rt(t)->gpu_fb_param_a,
+						tsk_rt(t)->gpu_fb_param_b,
+						observed);
+		
+		if(_fp_to_integer(fb->est) <= 0) {
+			// TODO: talk to Jonathan about how well this works.
+			// Maybe we should average the observed and est instead?
+			TRACE_TASK(t, "Invalid estimate. Patching.\n");
+			fb->est = _integer_to_fp(observed);
+			fb->accum_err = _div(fb->est, _integer_to_fp(2));  // ...seems to work.		
+		}		
+	}
+
+	TRACE_TASK(t, "GPU est update after (dist = %d, obs = %llu): %d.%d\n", 
 			   tsk_rt(t)->gpu_migration,
+			   observed,
 			   _fp_to_integer(fb->est),
 			   _point(fb->est));	
 }
 
 gpu_migration_dist_t gpu_migration_distance(int a, int b)
 {
-	// GPUs organized in a binary hierarchy, no more than 2^MIG_LAST GPUs
+	// GPUs organized in a binary hierarchy, no more than 2^MIG_FAR GPUs
 	int i;
-	int level;
-	int max_level;
+	int dist;
 	
-	if(unlikely(a < 0 || b < 0)) {
-		return MIG_LAST;
+	if(likely(a >= 0 && b >= 0)) {
+		for(i = 0; i <= MIG_FAR; ++i) {
+			if(a>>i == b>>i) {
+				dist = i;
+				goto out;
+			}
+		}
+		dist = MIG_NONE; // hopefully never reached.
+		TRACE_CUR("WARNING: GPU distance too far! %d -> %d\n", a, b);
 	}
-	
-	if(a == b) {
-		return MIG_LOCAL;
+	else {
+		dist = MIG_NONE;
 	}
 	
-	for(i = 1, level = 2, max_level = 1<<MIG_LAST;
-		level <= max_level;
-		++i, level <<= 1) {
-		if(a/level == b/level) {
-			return (gpu_migration_dist_t)(i);
-		}
-	}
+out:
+	TRACE_CUR("Distance %d -> %d is %d\n",
+			  a, b, dist);
 	
-	WARN_ON(1);
-	return MIG_LAST;
+	return dist;
 }
 
 
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